1. Field of the Invention
One embodiment of the present invention relates to an input/output device.
2. Description of the Related Art
In recent years, technological development of a device having a function of outputting data and inputting data by using incident light (such a device is also referred to as an input/output device) has been promoted.
An example of the input/output device is an input/output device that includes a plurality of display circuits and a plurality of photodetector circuits (photosensors) arranged in a matrix (column×row directions) and provided in a pixel portion and has a function of sensing the coordinates of an object overlapping with the pixel portion by sensing the illuminance of light entering the photosensors (coordinates-detecting function) and a function of generating image data of the object (capturing function) (see Patent Document 1, for example). In the input/output device disclosed in Patent Document 1, a photodetector circuit is constituted by a photodiode, an amplifying transistor, an initializing (reset) transistor and a selection transistor.